We all have a lot of theories about what's going to happen in Star Wars: The Last Jedi, and most of those theories are probably going to be wrong. It's not like Lucasfilm to come out and debunk a rumor, but that didn't stop John Boyega from basically revealing a story detail to Digital Spy. Light spoilers ahead.
There is a theory that Rey (Daisy Ridley) is not the only Force-sensitive person in the main cast, and that the Force could be with Boyega's Finn, as well. Digital Spy asked Boyega if he wanted Finn to be a Jedi, and this was his response:
"Would I like to be a Jedi? I think it would be more interesting if they had more than one person be a Jedi – but I think that that is the one of the unspoken laws of Star Wars. They only have one who has to go away and train."
So it sounds like Finn isn't going to end up being Force-sensitive — but that doesn't mean Boyega thinks Finn can't do something interesting in the Star Wars universe:
"I hope it takes an interesting turn; not in terms of being a Jedi, but there are loads more stronger characters in the Star Wars universe that can go up against Jedi and they don't necessarily have to be a Jedi. I would like to explore that more; the whole Boba Fett vibe. I would like to explore that for Finn, but who knows?"
Boyega is skirting around giving us any actual answers, but there are still a bunch of interesting directions they could take Finn's character.
Summary: Having taken her first steps into a larger world in Star Wars: The Force Awakens (2015), Rey continues her epic journey with Finn, Poe and Luke Skywalker in the next chapter of the saga, Star Wars: The Last Jedi.
Star Wars: The Last Jedi, directed by Rian Johnson, stars Daisy Ridley, John Boyega, Mark Hamill, Oscar Isaac, Carrie Fisher, and Adam Driver. It will be released on December 15th.